With a positron emission tomography apparatus (hereinafter referred to as ‘PET apparatus’), a positron-emitting labeled substance is administered into a subject, and also coincidence counting is carried out of radiation generated in a measurement-subjected part of the subject accompanying electron-positron pair annihilation, and the spatial distribution of the radiation concentration in the measurement-subjected part is measured and made into an image, and hence for example changes in the amount accumulated of the labeled substance in a specific region of interest of the measurement-subjected part are studied; PET apparatuses are being applied to the evaluation of drugs for Alzheimer-type or vascular-type dementia and so on.
FIG. 10 is a block diagram showing the constitution of a conventional PET apparatus. The PET apparatus 100 has a detection unit 101, a data collection unit 102, an image reconstruction unit 103, and an intravenous injection unit 104. Here, the data collection unit 102 has a frame-dependent histogram count memory 105.
A description will now be given of the operation of this PET apparatus 100. Firstly, a labeled substance T is intravenously injected into a subject S (for example a monkey) using the intravenous injection unit 104. Next, the measurement-subjected part H (for example the head) of the subject S is inserted into a measurement space within the detection unit 101, and then coincidence counting of radiation emitted by the labeled substance T that has reached the head of the subject S is carried out by the detection unit 101, and the coincidence count data is transmitted to the data collection unit 102. In the data collection unit 102, the transmitted coincidence count data is accumulated in the frame-dependent histogram count memory 105, and is summed in accordance with the image frame. The summed data is then sent to the image reconstruction unit 103, and based on this the radiation concentration distribution in the measurement-subjected part H of the subject S is made into an image.
In a drug evaluation test, after the labeled substance T has been administered, the drug being tested Y is administered to the subject S. Then, by carrying out numerical analysis of the radiation concentrations obtained as described above based on physiological constants characteristic of the subject S and so on, the change and so on in the accumulated amount of the labeled substance T in a region of interest of the measurement-subjected part H between before and after the administration of the drug being tested Y is obtained.